Development and verification of a local wind prediction model for efficient use of wind energy

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Kyoto Protocol to the United Nations Framework Convention on Climate Change will take effect, and Japan is demanded to considerably reduce the emission of carbon dioxide. Thus the use of wind energy will be important. For the efficient use of wind energy in Japan, wind prediction with high accuracy over steep and complex terrain is necessary.In the present study, a new local wind prediction model has been developed, which is based on the fundamental equations of fluid dynamics and can accurately predict separated flow field over complex terrain. In order to calculate wind flow over continuous real terrain, a new method for treatment of side boundary was proposed to assure the mass conservation at any cross section. It was found that the overestimation or underestimation of wind speed arising from the conventional method is improved and predicted wind speed by the present method shows good agreement with the wind speed obtained from calculation on whole domain. At an inlet boundary, a domain of same size as the computational domain was added to account for the effect of upwind terrain. For the engineering practice, a modified residual cutting method (Modified RCM) was proposed, which enables the equation to be solved quickly and stably and is as fast more than 20 times as conventional iterative methods. Finally, a large wind tunnel test with the real terrain model was carried out and characteristics of flow field over complex terrain were investigated by the model. It was noticed that the speed-up and speed-down due to convergence of terrain and flow separation was favorably demonstrated and prediction error of the present model was about ten percent. As a result, the present model can be used for the practical wind energy prediction and contributes largely to the wind energy exploitation in Japan.